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Show Table 1. Burner Geometry Parameters Factor A B C D Geometric Parameter Flame holder angle Fuel injection diameter Fuel injection location Swirl angle Factor Levels 30°, 90° 0.1", 0.3" 1.25", 4.25" from base of flame holder 30°, 60° A factorial experiment is one in which the effect of two or more factors on a measured response is of interest. Levels are the values of the factors used in the experiment. Thus, the model studies four factors (A, B, C, and D ) with the levels of each factor being purposely, rather than randomly, selected (Milton and Arnold, 1995). The responses to be analyzed are C O and N O x concentrations and combustion efficiency, r|. The rj is a function of C O , H C and CO2, the more C O and H C produced, the less efficient the combustion system. The results can be used as baseline data for comparison against future tests. The operating condition is fixed by the following limits: 3%02, 1.5MM BTU/hr load, 1800 - 2000°F stack temperature range, 0.08 - 0.20" H 2 0 furnace pressure range, and exhausting continuously out the rear stack. The results are analyzed using analysis of variance (ANOVA), "a procedure in which the total variation in a measured response is partitioned into components which can be attributed to recognizable sources of variation" (Milton and Arnold, 1995). Arellano et aL (1997) explained the theory behind the analysis, detailing the statistics used. Generally the effect of a parameter or combination of parameters can be isolated if a response to any parameter or combination of parameters deviates from a normal (Gaussian) distribution set forth by the Central Limit Theorem. A normal probability plot gives a visual representation of any deviation from a normal distribution, signifying that the effect of that parameter or combination of parameters is not truly random. RESULTS AND DISCUSSION The results of the DoE are summarized in the following table. The NOx is quite high because of the high temperatures. Although the stack temperature ranges from 1800 - 2000°F, the reaction temperatures would be higher than that, leading to greater N Ox production. 4 |